The present invention generally relates to fuel-fired fluid heating devices and, in a representatively illustrated embodiment thereof, more particularly provides a fuel-fired water heater having a specially designed single-pass condensing type heat exchanger incorporated therein.
Conventional fuel-fired water heaters are typically of a “single pass”, non-condensing configuration, meaning that the hot combustion gases used to heat the tank-stored water are subjected to only a single pass through a heat exchanger structure (usually a vertical flue) within the tank before being discharged from the water heater to, for example, an external vent structure, and that flue gas condensation does not occur to any appreciable degree in the heat exchanger structure within the water heater tank. In this conventional type of fuel-fired water heater, the overall thermal efficiency is typically limited to about 80-85%. Various proposals have been made to provide fuel-fired water heaters with condensing type single-pass heat exchangers (i.e., in which flue gases condense within the heat exchanger). However, previously proposed single-pass condensing type heat exchange structures incorporated in fuel-fired water heaters typically provide the water heaters with maximum thermal efficiencies limited to the 85-90% range.
It would be desirable to provide a fuel-fired water heater with a single pass heat exchanger having a heat transfer efficiency of at least ninety five percent and preferably greater.